The invention relates generally to integrated circuits, and relates more particularly to the cooling of integrated circuit chips. Specifically, the present invention relates to a heat conducting pad for chip cooling.
Efficient cooling of integrated circuit (IC) devices is essential to prevent failure due to excessive heating. Efficient cooling of the IC chips depends in large part on good contact between the chips and cooling blocks, because a major part of the heat resistance budget is expended between the chip and the heat sink block.
Conventionally, heat transfer between a chip and a heat sink is facilitated by providing a thin layer of thermally conductive paste disposed between opposing surfaces of the chip and the heat sink unit. Typically, the layer of paste is approximately 100 microns thick and is mechanically compliant to conform to the sometimes irregular surfaces of the chip and heat sink.
Such conductive pastes have generally proven to be reliable in facilitating heat transfer; however, the thermal conductivity of conventional pastes is generally limited (e.g., typical pastes have a thermal conductivity of approximately 5 W/mK). Thus, limited chip cooling is achieved. Furthermore, heavy cycling may cause non-uniform behavior in a paste, or may cause a paste to fail to thermally bond the chip to the heat sink, resulting in thermal run-away and also limiting chip cooling. Because a paste cannot be inspected during deployment or while in service, it is difficult to determine whether insufficient chip cooling can be attributed to failure of the paste. The use of a thermally conductive paste also complicates the repair of an IC device because it bonds directly to the device components, making removal of components difficult and time-consuming.
Thus, there is a need for a heat transfer apparatus that is capable of establishing reliable thermal contact, and of providing sufficient thermal conductivity and mechanical compliance between a chip and a heat sink.